from_kuid(9)

💅 from_kuid(9)

okay so bestie, welcome to the Kernel API Manual — this one's a lil function called from_kuid, and honestly it's giving "quietly essential" energy. Let's get into it 🫶

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🌸 NAME

from_kuid — create a uid from a kuid user-namespace pair.

Like, it literally builds you a uid out of a namespace-pair situation. iconic behavior tbh ✨

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🎀 SYNOPSIS

uid_t from_kuid (struct user_namespace *targ , kuid_t kuid );

Look at that signature. so clean. so deliberate. we love a well-typed moment 💖

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🦋 ARGUMENTS

• targ — the user namespace we want a uid in. like, where do you want your uid to live? this is that. the destination vibe 🗺️
• kuid — the kernel internal uid to start with. this is the raw ingredient, the starting point, the "before" pic if you will 🙈

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⭐ DESCRIPTION

so the whole thing here is: map kuid into the user-namespace specified by targ, and return the resulting uid. that's the assignment. that's the whole job. and it ate 💅

lowkey important detail: there is always a mapping into the initial user_namespace. no cap. that one's guaranteed, it's the safe home base 🏠

⚠️ and here's the part where you pay attention bestie: if kuid has no mapping in targ, then (uid_t)-1 is returned. that's your "nope, not found" signal. not a crash, not a vibe, just (uid_t)-1. periodt 💀

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🌈 SEE ALSO

Kernel file ./kernel/user_namespace.c, plus the whole friend group of related calls — go say hi 👋

• make_kuid(9)
• from_kuid_munged(9)
• make_kgid(9)
• from_kgid(9)
• from_kgid_munged(9)
• make_kprojid(9)
• from_kprojid(9)
• from_kprojid_munged(9)
• verify_root_map(9)

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k that's the whole page, bestie — you're officially a namespace girlie now 🧚‍♀️💜

signing off from ./kernel, dated October 2026, page from_kuid(9) — mwah 💋🎀